Method of making rubber articles



March 19, 1935. w. E. GARDNER 1,994,7{53

METHOD OF MAKING RUBBER ARTICLES Filed Au 27. 1931 Patented Mar. 19, 1935 PATENT OFFICE METHOD OF MAKING RUBBER ARTICLES William E. Gardner, Watertown, to Gardner Toy Company,

Mass., assignor Inc., Water-town,

' Mass., a corporation of Massachusetts Application August 27,

5 Claims.

The present invention relates to the production of rubber articles, and more particularly to hollow, seamless articles of rubber which are molded upon a form subsequently removed from within the article.

I have developed a method which results in the rapid and economical production of hollow rubber articles such as toy balloons, hot water bottles, and various other articles of like nature. I accomplish my purpose through the employment of a rubber latex suspension which. is caused by immersion or dipping of a sheet form therein to build up the required thickness of rubber upon the form. After such building up the rubber covering is cured at temperatures suificiently low to avoid destruction of the form, and the article is removed either by collapsing the form or by distension of the article to free the form therefrom.

I have discovered in the case of toy articles of rubber such as balloons in various shapes designed for inflation purposes that the forms may be died or stamped out of sheets of paper or equivalent material such as textilematerial. Having then treated the form to avoid penetration by the latex suspension, it can be coated by immersion, and thereafter the form removed either by crinkling in a manner to permit its withdrawal, or by distension of the rubber covering, or both. Inasmuch as the form is inexpensive and cheap to make, it is not essential to the process that care be taken to avoid destruction of the form after use. p

In the accompanying drawing illustrating the preferred form of the invention, Fig. 1 illustrates a stamping of a form from a sheet of paper; Fig. 2 represents the insertion of the form in a holder for dipping or immersing in a bath of latex suspension; and Fig. 3 represents the coated form with the mouth portion of the covering rolled up to provide a reinforcement prior to removal of the form therefrom.

As shown more particularly in the illustrated embodiment of the invention, a plurality of sheets may be simultaneously died out from a block or pad of sheets, thus promoting economy in the production of the forms. As indicated, the sheets of paper are shown at and the paper form stamped therefrom at 12. After cutting to proper shape and dimensions, the paper form at one end (in the illustrated embodiment of the invention the small end 14) is assembled with a slotted peg or holding clip 16, having a slot 18 formed in one end of curved formation to permit insertion of the end of the form and prevent ac- 1931, Serial No. 559,704

cidental displacement during handling. Having thus assembled the form with the holding peg, the form is dipped in a mixture intended to serve as a filler and at the same time promote coagulation and building up of the latex thereon. This I accomplish through the employment of a suspension of clay and calcium chloride in water, the clay filling the paper and preventing penetration by the rubber, and the calcium chloride serving to initiate coagulation of the rubber on 10 the form. By so preparing the form, penetration of the rubber is avoided, making it a simple matter to subsequently strip the covering from the form, and the necessary thickness of rubber covering may be built up upon the form through a single dipping. The thickness of the covering may be governed by the length of time or immersion, the concentration of the latex suspension, and the concentration of the calcium chloride bath.

Other loading or filling ingredients such as whiting, talc, soapstone, etc. in suitably divided form may be substituted for the clay. Any suitable coagulant known in the rubber art, such as acetic acid or sodium chloride, may also be employed in place of the calcium chloride to develop a film on the surface of the form.

After preliminary dipping, as above described, the form is removed and dried of surplus moisture. Thereafter the form is dipped in a latex suspension, the length of time being governed by the conditions as above outlined. This latex suspension is compounded in a manner which will be obvious to those skilled in the art, and has combined therewith the usual curing, coloring and loading ingredients in proper proportions. By the provision of a suitable accelerator the latex covering the form may be cured at atmos-' pheric pressure and with temperatures sufficiently low to avoid destruction of the form.

After building up a rubber cover of the desired thickness on the form, it is removed from the latex bath to a hot closet for the purpose of evaporating water from the latex suspension, and subjecting the article to elevated temperature for a suficient period of time to properly cure the covering. Having thus cured the covering, the open or small end is preferably rolled for reinforcing and the form removed from the holding peg. Thereafter designs, if any, may be imprinted upon the surface of the article, and the latter dusted with talc or a similar ingredient to remove any impression of tackiness from the surface. When completed, the article is removed from the form either by crinkling the latter to a small compass suflicient to permit its removal through the small end, or by distension of the article through the employment of compressed air which facilitates stripping of the form from within. Obviously, due to the inexpensive character of the form, no care need be taken to avoid its destruction on removal.

On certain types of articles the deposited film of rubber may be stripped from the form before curing, and thereafter the formed article cured in the usual manner. It is evident, therefore, that the present method is not confined to the curing of the article on the form.

It will be evident from an inspection of the drawing that the type of article actually formed by one embodiment of my invention comprises a circular head 20, having a face designated thereon, with protruding ears 22. After the completion of the article and upon inflation, the head expands greatly in size, the ears retaining substantially the same dimensions and becoming comparatively smaller with respect to the size of the head. It develops that upon inflation and distension of the head, a portion of the covering forming the ears is actually drawn into the head under tension, and furthermore the provision of the extending ears or the like appears to insure against rupture of the article during inflation due to the additional elasticity provided through the material contained in the ears themselves. Because ,of this decided advantage, I feel that the formation of a fiat, tubular form designed for inflation into a generally rounded or globular form, and having integrally extending projections communicating therewith and designed to furnish elasticity to the main portion of the form is a desirable and advantageous feature of my invention.

Although the present method is illustrated in connection with the production of thin wall balloons and similar small articles of manufacture where the thickness of the wall may approximate ten thousandths of an inch, nevertheless it should be understood that it is not confined to this class of articles, and that the essential features of the invention are'equally well adapted to the production of other hollow tubular articles of rubber such as inner tubes for automobile tires, hot water bottles, and the like.

It should be furthermore understood that although treated paper in sheet form is well adapted for the production of forms, nevertheless other sheet materials such as textile fabric are adapted for the purpose, and in some cases, owing to their greater strength, may be employed to advantage.

What is claimed is:

1. The method of making hollow rubber articles which consists in the cutting of a form of proper contour from a flexible sheet of paper, treating the paper form to avoid impregnation by rubber, thereafter enveloping the form in a covering of rubber by immersion in a bath of latex suspension, and subsequently curing the rubber covering.

2. The method of making hollow rubber articles which consists in the cutting of a form of proper contour from a flexible sheet of paper, treating the paper form to avoid impregnation by rubber, thereafter'enveloping the form in a covering of rubber by immersion in a bath oflatex suspension, and subsequently stripping from the form after curing.

3. The method of making hollow rubber articles which consists in simultaneously cutting a plurality of forms of predetermined shape from a stack of paper sheets, assembling the cut-out form to a holder, treating the form to prevent impregnation by the rubber and promote coagulation of rubber thereon, and immersing the treated form in a bath of latex suspension for a predetermined time to build up a rubber covering thereabout.

4. The method of making hollow rubber articles which consists in simultaneously cutting a plurality 'of forms of predetermined shape from a stack of sheets of flexible material, attaching each form to a holder, and immersing the form so attached in a bath of latex suspension to build up a covering of rubber completely about the immersed surfaces of the form, and thereafter by manipulation and distortion of the flexible form stripping the rubber covering therefrom.

5. The method of making hollow rubber articles which consists in impregnating a sheet paper form with a composition comprising a coagulant and a solid filling ingredient in divided form, and thereafter associating the thus treated form with a dispersion of rubber.

WILLIAM E. GARDNER. 

